Comments (12)

By Mom Unplugged, January 18, 2009 11:00 pm

Thanks to a suggestion from Meg at Bare Baby Feet, this week’s Unplugged Project theme is balance. We felt “sciency” this week, so my oldest daughter and I scoured our favorite science book but found nothing that sounded fun to her.

I did a few Google searches and happened across this amazing-seeming experiment. I tried it and then showed it to my children who were very impressed. As you will see, I tried to make it even more fun for kids by modifying it to make a balance toy: a flying bird. Read on for more!

THE SCIENCE:

This experiment (which I understand is often shown as a magic trick), involves two identical sharp forks, a real cork (a real one is a bit softer and easier to use than a plastic one), a toothpick, and a glass. Push the forks into the sides of the cork.

They should be in the middle of the cork, directly opposite each other. The cork will not be in alignment with the forks. Try to have the forks at a 90 degree angle to each other, like this:

Push a toothpick into the end of the cork, on the side between the forks (be careful, the toothpick breaks easily, so be gentle). You will have something like this:

Experiment by balancing the toothpick on your finger. It seems impossible, but once you find the right spot, the forks will just balance. You can mark that spot on the toothpick with a marker, or just remember about where it was.

Place the balance point of the toothpick on the edge of a glass. The forks should remain suspended on the side of the glass. Pretty amazing!

Now, for the grand and very dramatic finale! Take a match and light the end of the toothpick on fire (yes, I really did say to set fire to the toothpick - YOU, not your kids of course :-) ). The flame will move up the toothpick, burning it into nothingness. The fire will stop when it reaches the rim of the glass.

Does the cork fall down? NO! It stays put, hanging by practically nothing on the rim of the glass. You can even lift it off and place it back on, barely touching the rim, and the whole thing will balance.

Here’s a video I made of the toothpick burning (I have never put a homemade video on my blog before so I really hope it works). Watch closely and you’ll see that my son tried to knock the whole thing off the glass at the end of the video but it just bobbed up and down and returned to its original position. Very stable!

How does this seemingly magical “trick” work? Warning: science stuff coming up - feel free to skip to the next section if this is all “blah blah blah” to you.

The secret to understanding this experiment involves a study of center of gravity and pivot point. The center of gravity is “the point about which you can balance the object as if all the masses were concentrated or gathered at this point“ or “the average location of the weight of the object.” Imagine balancing a see-saw.

But the center of gravity does not necessarily have to be on the object itself. Here it is actually in the open space between the forks. This means that, unlike a see-saw, the object is not balancing on its center of gravity (“CG”). Instead it is balanced on a separate pivot point (the toothpick on the edge of the glass) away from the center of gravity.

We had to arrange the forks so that their mass was a bit lower than the center line of the cork in order to insure that the CG remained lower than the pivot point. Since the CG is lower, if the fork assembly is displaced, the CG will be raised and gravity will pull it back to equilibrium. You can see this in my video. All balance toys have a CG that is below their pivot point. (NOTE: I am NOT a scientist! Any physicists out there may disagree with my terminology, etc., but I am trying to make this as simple an explanation as possible.)

THE FLYING BIRD:

Not wanting to use my good forks as permanent bird wings, I had to think of something else. A matching pair of thrift store forks would have been ideal, but the thrift stores were all closed today. I ended up using a set of small screwdrivers that came from the bargain bin at the local hardware store, and that turned out to be not what my husband expected. There were four screw drivers, so by using two corks, my daughter and I were each able to make a bird.

We stuck them into the sides of the cork at the appropriate angles (see above). They were actually easier to get in there than the forks were.

TIP: Test “fly” your configuration on a glass before proceeding further. Adjust the screwdrivers (or forks) now if necessary to get it right. I didn’t check mine before-hand and had to fiddle later after the feathers were on.

To create a good surface for sticking on feathers, I cut construction paper into a symmetrical wing shape. By folding the paper and cutting double thickness (while keeping a portion of the fold intact) this was easy:

We then covered each screwdriver with a paper wing and stapled it so that the screwdriver was hidden inside. Staple as close to the screwdriver as you can so the wings stay on. It doesn’t matter if the staples are in the middle of the paper because you are going to completely cover the paper with feathers.

Paint your cork if you want to.

Next, glue on feathers. We had “natural-looking” feathers and “fake-looking” feathers, both from Walmart a long time ago. I opted for a colorful, fake bird. My daughter chose to be more natural. Elmer’s white glue didn’t work so well, so I broke out the hot glue gun and we began sticking on feathers.

I found an old jar to be a useful stand for our sticky birds while they dried, as well as for painting the underside of the cork.

After things have dried a bit, you’ll need eyes (googly or beads) and a beak of some sort. We cut the tips off some new crayons with scissors to make our beaks and they made perfect beaks! Glue them on with the glue gun.

If you haven’t already, carefully stick a toothpick in the back end of the bird.

Once everything is well dry, you can “fly” your birds on the edge of a glass. If properly balanced, they’ll bob up and down when touched, but won’t fall off. PLEASE don’t try the flame trick since you don’t want to risk setting all the glue and feathers on fire!

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If you did a balance project this week, then please link to your project post in Mr. Linky below. I really prefer links to project posts rather than blogs in general, so that readers will always be able to find your project no matter how far down it is buried in your blog. If you did not do a balance project, please do not link. Read more about how to participate here. We’d love to have you join us!

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The theme for next week’s Unplugged Project will be:

Ball

Have fun!

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Comments (12)

By Mom Unplugged, January 14, 2009 10:25 am

Thanks to a wonderfully creative music teacher at my children’s Montessori school, the latest fad around our house are little homemade guitars/harps like that shown above. The kids are loving putting different sized rubber bands around my food storage containers and then experimenting with the sounds produced.

The sound reminds me of a kalimba. It’s a little hard on me when I need to put away some food and can’t find any containers, but…oh well. I can adjust.

These simple little string instruments made me think that a post about quick and easy homemade musical instruments might be fun to write. I obviously won’t be anywhere close to covering all the homemade musical options, so if you think of something I forgot, please leave your idea in the comments.

If you are here because you are looking for musical instrument ideas, then be sure to read the comments for more ideas. Unplug Your Kids readers are very creative!

Here are my ideas:

• Let gourds or squash dry out. Once they are completely dry, the exterior will be hard and when you shake them, the seeds will rattle around inside. You’ll have some nice, natural maracas.

• Quick maracas: Fill plastic Easter eggs with rice or lentils and tape shut. Instant shakers!

• Paper plate maracas: Put some dried beans on a small paper plate. Cover with another, upside down paper plate. Staple the two plates together around the edges to seal them shut. Add a cardboard or popsicle stick handle if you want, then decorate. Here is ours:

• Wrap tissue paper around a fine tooth comb and make “Doo-doo-doo” noises through it for a kazoo sound.

• Flip over empty cylindrical cardboard oatmeal containers and bang on the bottom to make a drum.

• Line up a row of glasses and fill each with a different amount of water. Tap them with a spoon and note the different pitches. Play a tune!

• If you have a thin-rimmed wine glass, fill it with water. Wet your finger and rub it slowly and gently around the rim to create your own glass harmonica. It might take a bit of experimenting to figure out exactly what pressure you need, but the results are impressive. Experiment with more water in the glass and less water. What happens to the pitch? What about an empty glass?
  NOTE: Benjamin Franklin invented a mechanical glass harmonica like this modern one based on his design (he called it an “armonica”):

If you have never heard it, you must listen to the rather fairy-like sound of an armonica!

Can you play a tune with several glasses with different levels of water? You might not sound this good, but it’ll be fun!

• Blow across a glass soda or beer bottle like you would play a flute. Unless you play the flute, it’ll take a bit of practice. Adjust the angle of the bottle against your lips until you get it right. It will make a lovely tone. Different levels of liquid will produce different tones. What about lining up many bottles with different levels of liquid and playing a song?

(NOTE: Great related link - Bottled Music. This link tells exactly how much water is needed in a twenty ounce bottle to produce each particular note of the scale, and even has instructions for playing Row Row Row your boat on the bottles.)

• Craft idea: Cricket Chirping Sticks:

I didn’t think these sounded too much like crickets, but they do make a cool sound for your musical instrument collection! Learn how to make them here.

• Another craft idea: Sandpaper blocks - Wrap sandpaper around two blocks and attach it to the back with thumbtacks. For easier handling you might want to attach a knob to the back of each block (with glue or screws). Rub the blocks together for a cool sound. Try coarser and finer paper for different sounds.

And of course, the obvious: turn your 2 year-old loose in your pots and pans cupboard for lots of drums, cymbals and noise music.

That’s it for what’s in my brain right now, but Googling “homemade musical instruments” produces lots of cool results.

Here are links to a few of my favorites:

Jingle Sticks

Rainstick

Didgeridoo

Inventing Homemade Instruments with Math and Measurement (a wonderful website that teaches the science of music!)

Artists Helping Children (a very long list of many musical instrument craft links - useful!)

For a book that has some fun instrument games and activity ideas for young (preschool) children to use their homemade (or non-homemade) simple instruments, consider 101 Rhythm Instrument Activities: for Young Children by Abigail Flesch Connors:

NOTE: This is a great book to use with young children, older ones might find it boring.

Comments (16)

By Mom Unplugged, November 10, 2008 10:00 pm

Today, along with a visiting friend, we finally got to do this week’s kitchen Unplugged Project. We used cornstarch, a common kitchen ingredient, to create a non-Newtonian fluid. The other name for such a mixture is Oobleck, from the Dr. Seuss book, Bartholomew and the Oobleck.

It was SO COOL!! The kids and I found it fascinating! I was so enthralled that I felt that the mess (and there WAS mess), was actually very worthwhile.

I set out four small mixing bowls and spoons, one for each child. I also set out water, cornstarch, and measuring cups.

The kids each put about one cup of cornstarch into their bowl.

I had them add water just a bit at a time,

and stir until we got the “right” consistency.

It was probably close to about a half to two thirds of a cup of water, but the “right” consistency was quite obvious. When the mixture starts to feel hard to stir although it looks like liquid on the top, then it is probably about ready.

Test it by dipping your hand in, lifting out some fluid, and squeezing it into a ball. It should feel like a hard, dry ball in your hand but when you open your fingers, it will turn back into a liquid and run back into the bowl.

Here is a fleeting picture of it as a solid:

Adjust your mixture by adding a bit of water if too dry, or a bit of cornstarch if too wet. You’ll know you have it right when the oohs and aahs begin!

This was so much fun to play with and was a very weird sensation that is quite hard to describe. The children (including my 2 year-old) and I played for maybe an hour: squeezing, stirring, punching, and even hammering!

My favorite trick: If you roll it between your two palms as if you are making a ball with clay, it makes a nice solid ball, but as soon as you release the pressure, it all runs away!

Also, put a finger gently into it and it will slowly and strangely be sucked under as if in quicksand. Jab the finger in quickly, and it will hit a hard surface.

The Science:

As I understand it, when you squeeze the mixture, or compress it quickly in some way (hammer, punching, etc.), the molecules compress and become a solid. When the pressure is released, the molecules spread out again and the mixture becomes a liquid. As my oldest daughter said: “Oooo! I can feel it changing from a solid to a liquid!”

Here are two good explanations of what a non-Newtonian fluid is:

“Oobleck is often referred to as a ‘non-Newtonian’ substance because it does not behave as Newton’s Third Law of Motion states; for every action, there is an equal and opposite reaction. Applying this principle, you would expect Oobleck to ‘splash’ when you ‘smack’ it with your hand. (Smacking is the action, splashing is the reaction.) However, when you try this out Oobleck does not splash, in fact, it becomes a solid substance for a few moments.”

(from Oobleck - a Non-Newtonian Fluid)

or

“Isaac Newton defined normal liquids as having consistent flow behavior affected only by temperature or pressure; so fluids that change their resistance to flow (viscosity) under stress are not ‘normal’. Some of these fluids get runnier when stress is applied, like paint, toothpaste and slug mucus. Some get thicker, like quicksand and Oobleck.”

(from Science in the City - Bullet Proof Goo)

As to why it behaves this way, it seems that this is actually a matter of some controversy, but here are some links that are more knowledgeable than I:

Oobleck - a Non-Newtonian Fluid

More About Liquids: Thick and Thin

Fun:

You can actually walk on this stuff! My son wanted to try it after seeing this You Tube video.

(There are a few other walking on cornstarch videos out there if you are really into this!)

Tips:

1) I STRONGLY recommend that you either do this outside in an area that you can just hose off afterwards, or use a vinyl tablecloth that you can remove and hose off afterwards. Why didn’t I use mine?

2) Be sure to add the water a bit at a time, it is easy to overdo it.

3) If you do forget the tablecloth like I did, you will find that non-Newtonian fluids can be difficult to clean off a table. When you try wiping what looks like liquid, it turns into a solid and sticks.

When you stop scrubbing it returns to a liquid state! After a bit of frustration I used my science brain and poured water on the table. I was able to wipe the now runny cornstarch liquid into a trash can.

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Although I suggested it humorously yesterday, I have actually had several votes for an Unplugged Project theme next week involving “sort, trash, junk, donate.” Well, why not??

As Captain Jean-Luc Picard would have said (see, I haven’t always been without a TV!): “Make it so.”

Let’s call next week’s theme:

Sort-Junk-Donate

Remember, the theme can be loosely interpreted if you don’t feel like cleaning your house this week. Just be creative and have fun!

Comments (19)

By Mom Unplugged, October 5, 2008 8:32 pm

The theme for this week’s Unplugged Project was white. This was a really hard one for me!

I spent the whole week thinking: “I pick the themes, so why on Earth did I pick white??” All my kids could think of was white paint or marshmallows, but unfortunately we had neither in the house today when it got down to the wire for doing the project or giving up.

I figured there was bound to be a way to make homemade white paint so I googled “homemade paint.” I came upon this neat web page: Homemade Art Tips - How to Make Paint for Craft Projects.

As I read through the paint recipes, I came across an intriguing one for Crystal Paint that required only hot water and Epsom salt (isn’t salt white?), both of which I had. Further googling for “epsom salt paint” also led to this teacher discussion board post about salt paint.

This Salt Crystal Paint is simply a salt water solution that you brush on paper. After the water dries, the salt crystals remain and produce a glittery effect.

My kids and I were excited to try it and we decided to really experiment. We got out the Epsom salt, construction paper, crayons, scissors and hole punches.

We began by making construction paper “snowflakes” to use as stencils. The idea of glittery snowflakes was quite appealing on this almost wintry day.

We used the shaped hole punches on our stencils too.

We also colored some pictures on the dark construction paper using crayons.

To make the salt solution, mix about 1/2 cup Epsom salt with 1/2 cup hot water. I made mine by stirring the salt in on the stove.

We made one batch this usual way.

We also tried another way by adding LOTS of salt until we could add no more thus making a solution that was supersaturated (I snuck a bit of science in here!).

We stuck our stencils down with tape, trying to keep them flat, but without using so much tape that they would be difficult to remove later.

The first batch of “paint” looked like plain water and I didn’t hold out much hope for success. But we painted it on our stencils and our pictures anyway, then let them dry.

Here we are peeling off the stencils:

The effect was really cool! It is quite difficult to show in a photo, but when you look at the pictures under a light or in the sun, they really sparkle like snow!

We did one picture with the supersaturated solution and it came out thickly crusted with salt. There wasn’t much sparkle, just a flat white effect. In fact the white almost completely hid the crayon:

We preferred the milder 1/2 cup salt and 1/2 cup water version, but the supersaturated one would be great to use as a paint on its own. You could achieve some interesting looking white textures with a bit of experimentation. The brush strokes really showed up well, as you can see in the photo above.

A fun variation that we’ll have to try another day, is to add food coloring to the solution. This will create colored crystals!

[NOTE: In case you are unfamiliar with it, Epsom salt is the common name for magnesium sulfate. It can be found in most pharmacies since it is often sold as a soak for feet or for adding to a bath. I have also seen it in the garden section of Walmart since it can be used as a fertilizer. Roses love it and that is how I use mine! It is usually in a milk carton-type container, but I have also bought it in a resealable plastic bag.]

I imagine that this project works better with Epsom salt than table salt since the crystals are much larger. I wonder if Kosher salt or sea salt would work too? That would probably cost a lot more though.

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Did you do a white Unplugged Project with us this week? If so, then please put a link to your white project in Mr. Linky below. Please remember, this week’s Mr. Linky is only for white projects.

If you didn’t do a white project but are interested in future Unplugged Projects, then please DO NOT link, but read how to join in here. We’d love to have you!

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The theme for next week’s Unplugged Project will be:

Smooth

Enjoy!

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Comments (13)

By Mom Unplugged, September 29, 2008 3:53 am

This week’s Unplugged Project theme was fruit. We tried a really cool fruit project that was less than successful. I would have posted about our failure, except that I KNOW it can succeed since I did it successfully as a child. It needs a bit more fiddling (so we’ll keep working and post when it is perfected).

Instead I’ll post about a fruit science project from our book 730 Easy Science Experiments: With Everyday Materials. My oldest daughter found this in the book last week and for some reason was desperate to do it: polishing pennies. (I reviewed this book here if you want to know more.)

The idea is to show how lemon juice (very acidic) can clean the oxidization off a grungy old penny. If you live outside the US, any copper coin will work for this.

We ratcheted this one up. I had always heard that Coca Cola was acidic enough to strip enamel off teeth and polish stainless steel sinks, so a comparison test seemed in order. I had a Coke in the fridge from leftover guests so we gave it a go.

I was hoping that the Coke might perform up to the standard of the lemon juice and prove once and for all that it is BAD for your teeth.

Here are the ingredients:

Squeeze the lemon (pretty fun):

Put some lemon juice (and some Coke-if you choose to try the comparison experiment) into separate bowls and drop pennies into each bowl:

Leave them for 15 or 20 minutes then remove and compare:

We probably should have kept a “control penny” for comparison (actually, you can see the originals in the “ingredients” photo) but trust me, the lemon juice pennies were like new! The Coke pennies only slightly shinier. So much for my anti-Coke campaign.

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What did you do this week for fruit? If you joined in this week’s fruit project, then please leave a link to your project in Mr. Linky below. If you want to learn how to join in the Unplugged Project, then please read more here.

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Next week’s Unplugged Project theme will be:

White

Enjoy!